The long-term goal of the proposed methodological research is to improve the validity of data on the prevalence of heroin use and other highly stigmatized behaviors. This goal is pursued via the development and preliminary evaluation of the "item-count/paired-lists" technique, which was recently developed by the staff of the Social Research Group Like "randomized response" and other survey-based modes of indirect estimation, the new technique is designed to preserve respondent privacy and to reduce the problem of "respondent denial" in surveys covering sensitive topics such as heroin use. Unlike the previously developed techniques, however, the "item-count/paired lists" approach appears to be as easily applied by interviewers as direct questions--and as acceptable as the direct-question format to virtually all respondents. The first year effort, funded by the National Institute on Drug Abuse and now nearing completion, included development and preliminary evaluation of this technique in terms of the lifetime prevalence of heroin use; i.e., the key measure estimated was the percentage who had ever tried this drug. Based on the success experienced in this phase of the research, a continuation phase is proposed here in order to explore the feasibility of adding "branching questions" to the "ever-use" estimation sequence. The branching questions, designed to gather data on additional measures of heroin use, will again be incorporated into the technique, so that no one can ever know whether or to what extent the respondent has used heroin. The drug use measures which will be the focus of this phase of the research are: (1) lifetime frequency of use, i.e., the number of times respondent has used the drug during the course of his/her lifetime; and (2) recency of use, i.e., how long ago the respondent's most recent use of the druc occurred. Dataon lifetime frequency allows differentiating, e.g., "experienced" user from experimental" one-or-two time users. Data on recency of use allows estimation of past-year prevalence and "current use" (i.e., use during the month prior to interview). The proposed work includes development and qualitative evaluation based on a series of pretests in normal and high-drug-use areas, as well as a relatively inexpesive large-sample test of the technique's performance.